The present invention relates to a replenishing device for a closed circuit comprising: at least one hydraulic motor having a casing which defines an internal space and in which a cylinder block is disposed; and at least two main pipes which are connected to the pump and which constitute respectively a feed main pipe and a discharge main pipe for the motor; the replenishing device comprising a replenishing selector suitable for putting the main pipe that is at the lower pressure in communication with a valve which itself communicates with an atmospheric pressure reservoir.
In such known devices, the selector makes it possible to tap fluid from that one of the pipes which is at the lower pressure, so as to direct said fluid towards an atmospheric pressure reservoir for the purpose of cooling it before it is re-injected into the feed circuit of the hydraulic motor. It is known that it is possible to use a replenishing selector and a valve that are constituted by two distinct elements disposed one after the other in the replenishing circuit. For example, those two elements are fixed to the casing of the motor, or else they are incorporated therein. Such a configuration is shown in Document DE-195 22 448.
Devices of that type are not entirely satisfactory because it is relatively complex to install them in the motor. In addition, any given device is adapted to a motor specially organized to receive it, i.e. having recesses for receiving firstly the replenishing selector and secondly the valve.
An object of the invention is thus to provide a replenishing device that is easy to install in the replenishing circuit, in particular by being fixed directly to the casing of the hydraulic motor, that is simple to adapt to various motors from the same range of motors without it being necessary to adapt the shape of the motor in order to go from one replenishing device having given characteristics to another analogous replenishing device having other characteristics.
In addition, the Applicant has observed that it can be inopportune to tap fluid from the feed circuit of the hydraulic motor for replenishing purposes under certain operating conditions of the motor. For example, that applies during starting of the motor, during which the pressure is low and during which tapping of fluid would delay powering up.
An object of the invention is thus also to provide a replenishing device that avoids tapping of fluid for replenishing purposes under certain operating conditions of the motor.
This object is achieved by the fact that the replenishing selector and the valve are united in the same replenishing valve unit having an inlet suitable for being connected to the main pipe that is at the lower pressure, and an outlet which communicates continuously with the atmospheric pressure reservoir, the valve being suitable for causing said inlet to communicate with said outlet when the pressure in said main pipe that is at the lower pressure reaches a given pressure threshold.
The replenishing valve unit of the invention is thus in the form of a hydraulic component that is easy to install in the circuit, in particular by being mounted on the casing of the motor, so that its inlet can communicate with the main pipe that is at the lower pressure. To prevent replenishing fluid from being tapped when the pressure in the circuit is insufficient, the valve opens only as from the pressure threshold. The valve is disposed between the inlet and the outlet of the replenishing valve unit, and it causes said inlet and said outlet to communicate with each other only when the pressure in the main pipe that is at the lower pressure is sufficient, so that the outlet of said replenishing valve unit can be continuously in communication with the enclosure in which the fluid to be cooled is injected.
The replenishing valve unit constitutes a hydraulic component such as a cartridge that can be handled as a single item.
Thus, to adapt the replenishing mode to the conditions applicable for a given circuit, it is necessary merely to modify or to change the cartridge, without having to act on the other hydraulic components of the circuit.
Advantageously, the replenishing valve unit further has a constriction suitable for being interposed between the inlet and the outlet of said valve unit, when said inlet and said outlet are connected together via the valve.
The assembly formed by the valve and by the constriction constitutes a regulator for regulating the flow rate of fluid tapped by the replenishing device. Thus, the tapped fluid flow rate is zero until the pressure in the main pipe at the lower pressure reaches the pressure threshold. It then increases to reach a limit flow rate limited by the through cross-sectional area of the constriction. During this stage in which the flow rate increases, cooling of the circuit is progressively facilitated accordingly.
Advantageously, the outlet of the replenishing valve unit is connected to the atmospheric pressure reservoir via the internal space of the motor.
In which case, the fluid tapped for the replenishing also serves to flush the internal space of the casing of the motor. The fluid tapped by the replenishing valve unit is injected into the casing, while the fluid present in the casing of the motor is removed therefrom via the usual leakage return orifice. Limiting the flushing flow rate by means of the through cross-sectional area of the constriction offers the advantage of avoiding generating any undesirable excess pressure in the casing of the motor.
Preferably, when the replenishing valve unit also serves for flushing purposes, it constitutes a cartridge which is fixed directly to the casing of the motor. Thus, with a standard xe2x80x9cmotor bodyxe2x80x9d, it is possible, merely by changing the cartridge forming the replenishing valve unit, to choose the replenishing mode and flushing mode best suited to the use in question.
For example, it is possible to design a range of motors having in common the fact that their casings all have bores suitable for receiving such a valve unit, but differing from one another by parameters such as maximum cubic capacity, maximum torque, number of active operating cubic capacities, etc. Then the replenishing valve unit of the invention may be put in place on any one of the motors of the range in the bore provided for this purpose. If it is necessary to use replenishing valve units having different operating parameters (in particular as regards the calibration of the valve) for different motors of the same range, then no modification of the motors is necessary, but rather it is necessary merely to adapt the valve unit without modifying it externally (in particular by modifying the shape of the valve and/or the calibration of its return means) in order to obtain the desired operating parameters.
In an advantageous embodiment, the replenishing valve unit comprises a valve body and a replenishing slide, the valve body having two inlet ports respectively connected continuously to respective ones of the two main pipes and an outlet port that communicates with the atmospheric pressure reservoir, the replenishing slide being mounted to slide in the valve body by being controlled by the fluid pressure at said inlet ports acting against return means for returning the slide, so that said slide is caused to move between a neutral position in which it isolates the inlet and outlet ports, and two replenishing positions, in which that one of the first and second inlet ports which is connected to the main pipe at the lower pressure is capable of communicating with the outlet port via communication means; said replenishing valve unit further has means acting, when the slide is in the replenishing positions, to close off said communication means so long as the fluid pressure at the inlet port that is connected to the main nine at the lower pressure has not reached a given pressure threshold.
This replenishing slide, which is controlled by the pressure difference between the two main pipes, constitutes simple means for connecting the valve unit outlet to that one of the two pipes which is at the lower pressure. It is by closing off the communication means between the inlet and the outlet, inside said valve unit, that the valve makes it possible to prevent fluid from being tapped for replenishing purposes so long as the pressure has not reached the given pressure threshold.
Advantageously, the valve has a first pressure threshold as from which said valve causes the inlet and the outlet of the replenishing valve unit to communicate when said inlet is connected to the first main pipe and a second pressure threshold different from the first pressure threshold, and as from which said valve causes the inlet and the outlet of the replenishing valve unit to communicate when said inlet is connected to said second main pipe.
The replenishing valve unit in this variant is adapted to a circuit comprising a reversible motor in which, depending on how they are respectively connected to the pump, the two main pipes may serve either for feed purposes or for discharge purposes. The fact that the valve has two different pressure thresholds makes it possible to adapt the replenishing to suit the operating conditions of the motor, depending on its operating direction. In particular, the motor may have a preferred operating direction which is related to an operating parameter that is intrinsic to the motor, such as its efficiency, which is better in one direction than in the other. For example, it may be a motor having two operating cubic capacities, of the type described in Patent Applications FR-A-2 588 616 and FR-A-2 780 850. In such a motor, in low cubic capacity mode, the distribution pipes that do not contribute to providing drive torque are connected to the discharge in the preferred operating direction, and they are connected to the feed in the non-preferred direction, in which they present resistive torque opposing the drive torque.
Advantageously, the replenishing valve unit has a first constriction suitable for being interposed between the inlet and the outlet of the valve unit when said inlet is connected to the first main pipe, and a second constriction suitable for being interposed between the inlet and the outlet of the valve unit when said inlet is connected to the second main pipe.
In which case, it is the flow rate of tapped fluid that differs depending on the operating direction of the motor.